This invention relates to the art of globoid screws for use as mainrotors in compressors, expanders and the like, and more particularly to a new and improved method and apparatus for making a globoid screw for such use.
One area of use of the present invention is machining mainrotors for single screw compressors or expanders, although the principles of the present invention can be variously applied. In a single screw compressor or expander the mainrotor is in the form of a globoid screw which has a helical groove defining a helical thread along the length of the rotor and is machined from a cylindrical body of suitable material, typically metal.
In the manufacture of such mainrotors, the machining process presents a number of considerations. It should, of course allow rapid cutting to reduce machining time in a manner avoiding undue tool stresses and wear. Advantageously the cutting tool should provide a high degree of variability in cutting action. In addition, it would be highly desirable to provide a machining process and apparatus whereby the final and desired mainrotor groove geometry is not dictated by or limited to the geometry, i.e. profile and shape, of the cutting tool, so that a given cutting tool has the potential to generate different mainrotor geometries and with different allowable tolerance definitions or goals.